1. Field of the Invention
The present invention relates to a scanning probe microscope technique and sample observation method using the same and device manufacturing method.
2. Description of the Related Art
As a technique for measuring minute three-dimensional shapes, a scanning probe microscope (SPM) is known. This is a widely employed technique whereby minute three-dimensional shapes of the atomic order can be measured, by scanning a sample whilst maintaining the contacting force at an extremely small value while controlling a probe with a sharp tip.
On the other hand, dimensional control using a CD-SEM (Critical Dimension SEM) is currently carried out in an LSI minute pattern formation process, but with the advance of pattern miniaturization, the pattern formation process is facing the following limits. (1) Problem with measurement accuracy. The gate width of a 65 nm node LSI, which is expected to become the mainstream in 2007, is 25 nm and if its allowable variation is assumed to be 10% and measurement accuracy is assumed to be 20% thereof, the required measurement accuracy is estimated to be 0.5 nm. (2) Demand for profile measurement. There is a growing demand for the introduction of APC (Advanced Process Control) for high-accuracy control of line widths and this requires a technique for measuring not only pattern wiring widths but also sectional shapes which have a considerable influence on electrical characteristics. (3) Problem with measuring target. There is a growing need for measurement of materials with low electron beam resistance such as resists for DUV (deep ultraviolet rays), low-k (low dielectric constant) film material.
It is difficult for the current CD-SEM to deal with the above described problems and requirements. For this reason, a scanning probe microscope technique seems to be a promising technique. What is required in this case is a scanning probe microscope technique applicable to a pattern having a large aspect ratio and an inclination of step locations of approximately 90 degrees.
On the other hand, Japanese Patent Laid-Open Publication No. 11-352135 discloses a method of scanning a sample while vibrating the sample or probe with certain amplitude to make the probe collide periodically with the sample and reduce damages to a soft, brittle sample and probe. Furthermore, Japanese Patent Laid-Open Publication No. 2001-33373 discloses a method of performing servo control on a probe at only discrete measuring points, measuring heights and moving to the next measuring point with the probe lifted. This method requires fewer contacts and has less damage to a soft, brittle sample and probe. This method does not drag the probe and thereby has an advantage of being able to measure shapes in step locations faithfully. Furthermore, Japanese Patent Laid-Open Publication No. 2002-206999 also discloses a method combining both operations.
However, there is a problem that the probe slips slightly in a steep incline and the measured shape is distorted even when the above described methods are used. Another problem is that the probe is worn due to the slippage of the probe and vibration of the probe.
In other words, it has been difficult for the techniques disclosed in the above described patent documents to measure shapes accurately because the probe slips slightly in a steep incline for a sample having a high aspect ratio, and the measured shapes are distorted. Furthermore, the probe is worn due to the slippage and vibration of the probe and it is difficult to measure the shapes stably and accurately.